1. Field of the Invention
The present invention relates to the field of machining and more particularly to adaptations of machine tool frames allowing to realise machining and more particularly milling under the best conditions.
2. Discussion of the Background
Classically, the workpiece is placed in front of a tool, such as a milling tool, turning at high speed and held by a frame fitted with slide blocks permitting a translation of the tool in relation with the workpiece. This rectilinear translation defines the generating trajectory of a plan on the workpiece after passage of the tool.
The stress and temperature rise generated by the cutting process, and in particular when the machine tool is a high-rate machine tool, create deformations and particularly deformations of the frame requiring until now the use of bulky components.
In fact, the lack of rigidity of a frame can lead to bad machining and must therefore be solved in particular when the size of the components and the speed of execution are such that the stress and deformations are increased. The need to obviate to the aforementioned problems is all the more important as the precision required for such machinings is more and more exacting. Consequently, a first solution consisted in oversizing the frames of machine tools submitted or that may be submitted to such deformations so that these deformations did not affect the precision of the machining achieved.
Another solution to eliminate the deformations due to the stress caused by cutting resides in the use of an actuator ensuring a stress on the frame of the machine tool in the opposite direction to the stress caused by cutting, which if it is well orientated, balances the mechanical forces system.
Another solution is revealed in French Patent Nxc2x0 2 701 881, which, by a subsiduary device, transforms an open-structure machine tool into a closed-structure machine tool. The open-structure machine tool is of the type of which comprising a vertical upright which moves along a slide block along the X axis, fixed on a base, said vertical upright comprising an overhanging crossbeam along which moves, along the Y axis, a spindle support moving along an axis orthogonal to the aforementioned axes, along the Z axis. To obviate the aforementioned inconveniences, said machine tool comprises an additional structure conceived to be situated at the level of its open side, fitted with a connecting device which slides along the said structure, said connecting device conceived to be linked to the free end of the said crossbeam so as to constitute a machine with a gantry with a closed-structure frame. Closing the structure of the frame enables to relieve the structure but also to measure the constraints applied to the said frame so as to work out and size under the best conditions the components of the frame.
The passage from an open-structure to a closed-structure enables therefore to do away with the stress and deformations due to machining operations.
The disdadvantage to the device described in the aforementioned patent resides in the fact that the structure enabling to close the frame and thus to balance the mechanical forces system constituted by the frame, is only additional. In fact, for access reasons, the additional structure is retractable and does not close permanently the structure of the frame.
In view of this situation, the applicant has carried out research on a new concept of arrangement of machine tools and in particular of milling machine tool ensuring the normal functions of a high-rate machine tool while obviating to the aforementioned disadvantages and in proposing a closed-structure frame.
This research has led to the novel conception of a machine tool adopting an original arrangement of its components.
According to the main characteristic of the invention, the machining machine tool of the type of those adopting a closed-structure frame, the machining being realised inside the frame, is remarkable in that the frame of the said machine tool adopts a C-shaped profile, the ends of the said C being linked by the operating head of the machine tool.
This characteristic is particularly advantageous in that it enables on one hand, to respect the need to get rid of the deformations due to the stress from cutting in offering a frame with a closed-structure, and on the other hand, in realising the closing of this structure indefinitely and by means of the operating head of the machine tool.
Furthermore, using the arrangement of the operating head inside the C shaped by the frame holding it, has for advantage to reduce the volume of the machining zone and thus to confine or to limit the zones subjected to the projection of swarf, liquid spurts and to a stale atmosphere. Also, this limitation of the machining zone enables an easier evacuation of the aforementioned effluents as well of an improvement in the casing.
The arrangement of the frame, adopting a C-shape, closed by the operating head of the machine tool has also for advantage to offer a machine tool dedicated to a forced manufacturing rate which, geometrically, forms a tunnel for passage of the workpieces.
According to another particularly advantageous characteristic of the invention, the machine tool is of the type of which the operating head is mobile and is remarkable in that each end of the branches of the C-shaped profile of the frame holds a slide block ensuring support and guide of the said operating head in its machining movements.
Therefore, the machine tool of the invention does not only close a C-shaped frame by means of its operating head but also offers to use judiciously the ends of the C formed by the frame to support the slide blocks which will ensure guiding of the operating head during its displacements.
In the mind of the applicant, the structure of the machine tool of the invention such as previously described and according to the advantages it brings, is particularly suited when the machining realised by the said operating head is milling.
The fundamental concepts of the invention having just been detailed hereinabove in their most elementary form, more details and characteristics will come out more clearly when reading the description hereinafter using as a non limitative example and having regard to the attached drawings, an embodiment of a machine tool in accordance with the invention.